Add license file

Change-Id: I2b64360a2c359333f6aa2383a355fc8f801a07b2
Add update logic for DataCard.

If a row exists for a DataCard, attempt to update it first when
publish() is called. If the card cannot be updated, create a new row to
represent it.

Change-Id: I5fd250ca9a508735257b8fcd549570ae32b66982
Complete implementation of publish and retrieval.

Abstract and refactor publish functionality by creating a
PublishableCard superclass. Complete publish/update/unpublish
functionality. Add support to retrieve DataCard and DataCardImage
objects from the ContentProvider data.

Change-Id: I898d363ea84b8675802b33db9dc444f7ec2ec322